Hydrogen peroxide –
Hydrogen peroxide (H2O2) is a clear, colorless liquid that is commercially available in a variety of concentrations ranging from 3 to 68%. H2O2 is considered environmentally friendly, because it can rapidly degrade into the innocuous products water and oxygen. Hydrogen peroxide is a strong oxidizer and is used as a bleaching agent, disinfectant, sterilization and antisepsis. H2O2 demonstrates broad-spectrum efficacy against viruses, bacteria, yeasts, and bacterial spores. In general, greater activity is seen against gram-positive than gram-negative bacteria; however, the presence of catalase or other peroxidases in these organisms can increase tolerance in the presence of lower concentrations. Higher concentrations of H2O2 (10 to 30%) and longer contact times are required for sporicidal activity
Mode of Action – Hydrogen peroxide works by producing destructive hydroxyl free radicals that can attack membrane lipids, DNA, and other essential cell components. Catalase, produced by aerobic organisms and facultative anaerobes that possess cytochrome systems, can protect cells from metabolically produced hydrogen peroxide by degrading hydrogen peroxide to water and oxygen. This defense is overwhelmed by the concentrations used for disinfection.
When hydrogen peroxide encounters bacteria, it quickly oxidizes some of the components of the outside of the bacteria. This can not only be toxic to them, but can punch holes in the membrane that the bacteria use to protect and contain themselves. As a result, the bacteria quickly die.
The time required for inactivation will be dependent on the concentration and the type of organism you are targeting. With a 3% solution the majority of the disinfecting is done within 10 minutes and will continue to disinfect for up to an hour or more afterward but with diminishing efficiency. As you go up in strength your exposure time decreases and a wider range of organisms are killed.
One of the advantages of using hydrogen peroxide as a disinfectant is that it is cheap, easy to find and safe in low concentrations. Hydrogen peroxide is most commonly available as a solution in water. For consumers, it is usually available from pharmacies at 3% and 6 % concentrations. At 20% and higher concentrations Hydrogen Peroxide needs to be used with caution and should be treated the same as a strong acid. http://www.cdc.gov/hicpac/Disinfection_Sterilization/7_0formaldehyde.html
Disadvantages – Hydrogen peroxide is light sensitive. It breaks down quickly when exposed to light so it generally comes in brown bottles that filter out the sun's rays. The rate of decomposition increases with rising temperature, concentration and pH. With cool, dilute, acidic solutions showing the best stability because low percentage (3%,6%) solutions are unstable, chemical stabilizers are added to the peroxide to keep it from breaking down before it can be used. Under normal conditions, hydrogen peroxide is extremely stable when properly stored. The decomposition or loss of potency in small containers is less than 2% per year at ambient temperature. It is also highly corrosive, at 20% or higher concentrations and can cause burns.
3% is commonly found in drug stores and occasionally 6% but usually has to be ordered by them. 16 oz. is usually under a dollar for 3%.
7% Hydrogen Peroxide – 1 case, 4 – 1 gallon – around $25.00 This is found online by companies that offer water treatment solutions to people who have self-supplied water systems.
35% Hydrogen Peroxide – 1 gallon – Starts at around $35.00 and goes up from there. You will have to do a lot of looking to find a source that will ship a 1 gallon container of 35% Hydrogen Peroxide. Shipping adds a good amount to the price because it is considered a hazardous substance at this concentration and amount.
Note : 20% - 35% can be found on line at companies that sell hydroponic, pool or agricultural supplies. Although these must be diluted, you are able to get the concentration/strength you require. Remember, at 20% and higher concentrations Hydrogen Peroxide needs to be used with caution and should be treated the same as a strong acid. 35% Hydrogen peroxide is extremely corrosive and a strong oxidizer. It can cause severe burns. Handle with care and keep out of reach of children. The vapor is extremely irritating. Avoid contact with skin and eyes. Do not take internally.